About The Generator Sizing Calculator

The Generator Sizing Calculator estimates generator kVA, recommended margin, and full-load current from running load, power factor, starting factor, derating, voltage, and phase.

How to Use the Generator Sizing Calculator Online

1. Enter running load, power factor, and the expected starting factor.
2. Set derating, voltage, and phase for the installation.
3. Run the calculator to review base demand, required kVA, margin, and current.

Choosing Options Correctly

Use realistic starting multipliers for motors and compressors, and reduce available capacity for altitude, temperature, enclosure, fuel type, and manufacturer derating guidance.

Common Use Cases

• Estimate standby generator size for a known load list.
• Compare starting-factor assumptions.
• Check approximate generator current at site voltage.

Quick FAQ

Does this include load sequencing?
Only in a simplified way, if at all. Starting large motors one at a time can change the required generator size.

Is the output final for purchase?
No. Verify with generator vendor data, starting kVA, transient voltage dip, fuel, altitude, ambient temperature, and duty rating.

Should I include nonlinear loads?
Yes. UPS systems, VFDs, rectifiers, and other nonlinear loads can require harmonic and alternator sizing checks.

Can I use it for large industrial systems?
Use it as an early estimate only. Large systems need load studies, protection coordination, controls, and vendor review.